The earliest spam--unsolicited commercial email--was sent in 1978. It has been a significant problem since 2000.
As of 2012, Spam has been slowly spreading to other types of digital human communications, although the vast majority of unsolicited commercial messages still go by email. Spam traffic over texting/SMS is growing, and it is sometimes sent over instant messages ("SPIM") and over internet telephony/Voip ("SPIT").
As of 2012, spam remains a major problem, and it appears likely to continue as such for the foreseeable future.--David Ferris